The 3GPP (Third Generation Partnership Project, www.3GPP.org) is a collaborative effort to produce technical specifications and proposals for third generation (3G) mobile systems. One of these proposals, the IP Multimedia Subsystem (Internet Protocol Multimedia Subsystems or IMS), is rapidly gaining acceptance by many as the de-facto standard for IP multimedia services for the 3G platform.
One of the key features of IMS is the use of the Session Initiation Protocol (SIP) for call control and signaling functions. SIP pertains to an RFC standard (RFC 3261) from the Internet Engineering Task Force (IETF), the body responsible for administering and developing widely received technical specifications that shape the Internet. SIP is also employed to facilitate the transfer of multimedia files, such as video clips, from one mobile device to another receiving equipment, such as the mobile device of another end user.
To transfer a video clip, a SIP proxy that is set up within the sender's handset is typically employed to send the video clip. For example, if the sender wants to send a video clip to a given recipient, the video clip is first loaded into the memory area of the user's handset. Using the SIP protocol, the SIP proxy therein then sends the video clip to the recipient using the recipient's identity, which is supplied by the sender.
Consider the situation wherein the user wishes to send the same video clip to a group of recipients (one-to-many) instead of to a single recipient (one-to-one). Again, the video clip is loaded into the memory area of the user's handset. The user specifies the identity of each recipient, and the SIP proxy in the user's handset sends the video clip to the recipients, one after another.
Although SIP-based approach accomplishes the one-to-many transfer of the video clip, there are many disadvantages. For example, although many modern handsets provide the ability to specify an address list, the list is typically employed for quick dialing. More specifically, the current address list cannot be employed by the SIP proxy to send the video clip to the members in the address list. Instead, the sender has to specify each recipient manually.
As another example, since the video clip is sent to the recipients one at a time, the bandwidth requirement between the sender's handset and the rest of the network is quite sizable. For example, if the user wishes to send a 5-megabyte video clip to 4 recipients, then approximately 20 megabytes worth of video data will be transmitted from the sender's mobile device. Since the wireless terminal link bandwidth (i.e., the bandwidth between the mobile device and the gateway to the rest of the network) is often the most limiting and expensive, such approach imposes a high bandwidth demand on the network's resources where the resources are most limited. This limitation severely restricts the scalability of the current approach.
As yet another example, the current approach for the one-to-many transfer of multimedia data may cause many of the recipients to receive the video clip minutes or even hours after the'start of video transfer session. For example, if a given recipient is the 10th recipient in the queue to receive the video clip, that given recipient may have to wait for the client application in the sender's handset to finish sending the video clip to the preceding nine recipients before starting to receive the video clip. For some real-time or near-real-time video streaming usage scenarios, the current approach is unsatisfactory since the time delay for recipients at or near the end of the queue would be unduly long.